The present invention relates to apparatus for dispensing biological materials and reagents; and more particularly to apparatus for dispensing glassy, porous reagent spheres into a laboratory vessel in which a reaction is to take place.
Few biologically active materials are sufficiently stable so that they can be isolated, purified, and then stored in solution at room temperature. As a consequence biological reagents often are provided in dried form to increase their storage stability. In preparing reagents for convenient and efficient testing of biological samples, it is frequently important to obtain dry chemical blends in uniform, discreet amounts. These reagents must be efficiently and economically prepared in small, precisely measured quantities for laboratory use.
One type of carrier which has been used to stabilize doses of biological reagents are glass-forming filler materials, such as a sucrose polymer. A measured amount of a biological reagent solution is incorporated into the filler material (which is a water-soluble or water-absorbing substance). The composite then is freeze dried to produce a reagent sphere having a composition which immobilizes and stabilizes the biological reagent. Examples of glass-forming filler materials for stabilizing biological reagents are described in F. Franks, "Long-Term Stabilization of Biologicals", 12 Bio-Technology 253 (1994); U.S. Pat. No. 5,098,893; U.S. Pat. No. 5,200,399; and U.S. Pat. No. 5,240,843.
The biological reagent spheres must be kept relatively dry during storage. Otherwise, moisture allows the filler material to change into a rubber state which causes the reagent contained therein to become unstable. As a consequence, reagent spheres must be stored in a container that prevents moisture from reaching them.
In order to use the reagent in a biological procedure or experiment, the carrier spheres have to be individually dispensed from the storage container. A dispenser for this purpose must have several characteristics. As noted previously, moisture adversely affects dried reagent spheres and thus the dispenser should be sealable to prevent moisture penetration between dispensing operations. Furthermore, the dried reagent spheres easily become charged with static electricity which causes them to cling to the walls of conventional dispensing apparatus. In addition, the dispensing apparatus has to individually meter out one reagent sphere at a time in a manner which does not crush the sphere. Because the diameter of the reagent spheres is not closely toleranced, the dispensing apparatus must be designed to accommodate spheres of varying diameter, if conventional spheres are to be accommodated.
It is also desirable to design the dispenser to avoid cross-contamination either due to use of a common dispenser with spheres containing different biological reagents or due to an outlet of the dispenser coming into contact with several laboratory vessels having different substances.